1. Technical Field
The present invention relates to a seal structure, a seal method, a liquid crystal device, a manufacturing method thereof, and a projector.
2. Related Art
In a liquid crystal device that is used as a light-modulation unit in a projection-type display device such as a liquid crystal projector, a sealing material is provided along a peripheral part between a pair of substrates and a liquid crystal layer is sealed in the center. An electrode for applying a voltage to the liquid crystal layer is provided on the insides of the pair of substrates. An alignment film is provided on the inner side of the electrode, and controls the alignment of the liquid crystal polymer when applying a nonselective voltage. Based on change in the alignment of the liquid crystal polymer when applying a nonselective voltage and when applying a selective voltage, light from a light source is modulated to produce image light.
A high-polymer film of polyimide with an added side-chain alkyl group whose surface has been processing by rubbing can be used as the alignment film. In this rubbing process, the surface of the high-polymer film is rubbed in a predetermined direction using a roller consisting of a soft cloth, so that the high-polymers are aligned in a predetermined direction. The liquid crystal polymers are distributed along the aligned high-polymers due to a reciprocal effect between the high-polymers and the liquid crystal polymers. That is, the liquid crystal polymers are aligned in the predetermined direction when a nonselective voltage is applied. The side-chain alkyl group imparts a pre-tilt to the liquid crystal polymer.
When a liquid crystal device including an organic alignment film is used as a light-modulating unit in a projector, there is a possibility that the alignment film gradually breaks down due to heat and strong light emitted from the light source. After the liquid crystal projector is used for a long period of time, the alignment control function of the liquid crystal polymers may deteriorate (e.g., the liquid crystal polymers may not be arranged at the desired pre-tilt angle), with a consequent deterioration in the display quality of the liquid crystal projector.
Accordingly, an alignment film consisting of an inorganic substance having excellent light-resistant and heat-resistant properties is being considered for use. Proposed methods for manufacturing an inorganic film include ion bean sputtering and diagonal evaporation (e.g., see Japanese Unexamined Patent Application, First Publication No. 57-157214). In these methods, particles of the inorganic substance are injected to a substrate at a predetermined incidence angle, forming an inorganic alignment film consisting of column-like structural bodies of the inorganic substance. In a liquid crystal device, the liquid crystal polymers are aligned along the column-like structural bodies of the inorganic alignment film. That is, the inorganic alignment film controls alignment and imparts a pre-tilt to the liquid crystal polymers.
To seal a liquid crystal layer between the pair of substrates, a seal material must be provided on the surface of the inorganic alignment film. However, since the inorganic alignment film consists of column-like structural bodies, the inorganic alignment is porous; hence there is a possibility that a comparatively large gap is formed at the interface between the seal material and the inorganic alignment film. When water, impurities, and the like from outside the liquid crystal device infiltrate the liquid crystal layer through this gap, they inhibit the alignment control function of the liquid crystal polymers, mainly in the liquid crystal device. This reduces the reliability of the liquid crystal projector.